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Topic Review (Newest First)

11-12-2004 03:30 PM

firebird_red

Yeah, it's marked 400 where you describe. The engine code marked on the right front of the block is "YS". The quadrajet has number showing that the carb is from a 70 pontiac. I'm told the engine is from a 71 with 96 heads.

Are there any more places to help ID things? I don't see any numbers on the distributor pad, but maybe the distributor is covering that up.

11-11-2004 09:41 PM

jimfulco

Are you sure it's not a 455 already? I think '71 GTO's came with a choice of 400 or 455 engines. Look on the driver's side of the block just behind the fuel pump & see if there's a displacement number cast into the block.

11-10-2004 01:13 PM

Claymore12

But spending other people's money is one of those things I do really well

And I like this place for engine hardware just because Ken is good about talking with you about what you want to do with your motor. Of course the same can be said for most of the widely known poncho shops- it's a rather welcoming community they seem to like newcomers as it's one more poncho on the road.http://www.pontiacdude.cc/

As for the new GM big cube motors- while I haven't personally tried to drop one into a poncho's engine compartment, I highly doubt it'd line up. It was a really big deal when a non-GM affiliiated company started turning out aftermarket blocks patterned after the Pontiacs- admitedly it was an aluminum block but it was still the first new "Pontiac" blocks since 1980- I think.

Don't underestimate your 400 it can be a very solid motor and would theoretically be cheaper since you already have it, since finding a 455 would require putting down $$ for the block and crank, if nothing else. The machine work would be mostly the same so if you fork over cash for a new block it certainly is that much you can't spend on something else. A Poncho 455 is simply more cubes and would drop right in. I can't honestly say when they stopped making the 455 but I don't think they stopped in '74 I think they made 455s up to/through '79.
If you have the cash to stroke your 400 it can be done for a "reasonable" cost- you've already noticed that reasonable in Pontiac terms isn't quite the same as small block chevy terms. There are also new aluminum heads being produced for the Poncho- and not just Edelbrock there are a couple companies in it now, that you might look into.

Keep in mind also that the stock iron heads for the 350s 400s and 455s readily interchange. You could get some huge chambered heads that would easily let you run 87 octane in a 400 stroked to 455 and still get yourself a decent compression ratio.

11-10-2004 12:10 PM

firebird_red

Claymore, thanks very much! That is what I wanted to know.. fitment. I had thought GM used the same engines across chevy, buick, pontiac etc so I figured getting a fresh engine might be the way to go. I figured that the Firebirds evil twin the Camaro was offered with a 350 and assumed it was the same as the Firebird 350 engine.

Rifraf, thanks for the advice on the 455 and the story about the one you built. It's that front end lifting power that sent me searching for the used bird. It is my wife's car so it must be street friendly with no drivablity quirks. A radical cam would not please her at all. It will never see the track but it surely will see plenty of WOT.

What would be the benefit of looking for a used 455 compared with building what I have? Wouldn't they both be in need of rebuilding? Any 455 I found in a yard will have been around in 1974 or earlier, wouldn't it?

Are the GM 455 crate engines also different from the Pontiac block, and therefore have the same fitment issues.

My priority is to have an engine that runs well on premium pump gas with some oomph and this engine should fit that bill if it were running right. My engine is out of a GTO, with the YS head. I think that was a lower power/lower compression version but I have more research to do.

Perhaps the solution would be to rebuild what I now have with the stroker kit.

I would appreciate some suggestions on reading material, parts suppliers etc. I talked with the owner of a 67 Firebird that was for sale and he showed me the receipts for all his engine work, saying how much extra it cost to build up a Pontiac. I'm starting to understand why.

Just so folks know, I don't have the tools, ability etc to do this work myself so I will be paying for others to attend to things. Price comes into major consideration for the project. Keep this in mind while you're vicariously spending my money... ;0)

11-10-2004 06:36 AM

Claymore12

uhmm, a zz4 or big block will NOT drop right in. It would work if you went through the hassle of swapping engine mounts and if you didn't place your motor mounts right, possibly trans mount and therefore the driveshaft.
The PONTIAC blocks are externally the same from the 326 up to the 455, don't confuse these with GM corporate blocks which are really just a small block Chevy. Buik, Olds, & Pontiac stopped using their own blocks around 1979ish give or take a couple/few years and some odd exceptions.

I do agree with rifraf in finding a 455 if you can, they would drop right in and give you more go. However there are readily available stroker kits to turn your 400 into a 455 and such engines are arguably stronger since they have less friction loss through the mains (smaller crank).

11-10-2004 01:49 AM

rifraf

Yea,a big block or a small block chev will go in,with a chev trans and mounts and such,its basically a camaro. For me,I would hunt for a early-mid 70s 4 bolt main pont 455,they're getting a little hard to find,look for wagons or big boats,they have both early and late mounts cast in and with a decent set of heads,cam,and headers and they are brutal. I threw one together with forged flat tops,70 stage 3 400 heads,a 280-.480 cam,headers,hei,and a stock intake for a friend in his 70 4spd formula and it jerked the front wheels of the ground with ease,and it looked stock,except the headers,and it ran smooth! ,well,a little lope,but not bad. We had some fun with it,ate up some guys,had em chase us down after watching there eyes bug out,then told em we we-rent sure what it was,said we got the motor from the wrecking yard for $325 and painted it! Thats always good for some parking lot conversation once ya leave,hee hee.

11-10-2004 12:48 AM

firebird_red

I bought a 68 firebird 400 that has a 71 gto engine in it that seems to have serious problems. The car was fetched out of a field after being parked for years.

The engine idles okay while belching lots of exhaust. When it's rev'd up in park, it vibrates really badly. I'm thinking that it may have a bent connecting rod or similar issue. I guess I have to get the engine out and apart to see; something to discuss with my mechanic friend.

Since the engine is not the "matching numbers" item for the car anyway, I'm thinking it really doesn't matter what engine goes back in.

Someone mentioned earlier that the 350/400 etc are all the same basic block. Would it make sense to just buy a new GM crate engine for the car or would it be better or cheaper to find a machine shop that can rebuild what is there already? Would the various GM crate engines such as the ZZ4 HO drop right in?

My goal is to restore the car to similar to stock appearance and performance. The rear won't be tubbed or anything like that, so there is a limit to how much HP this car can plant anyway.

10-27-2004 11:57 PM

rifraf

Well,what makes a 350 and a 400 different is the bore size,stroke is the same,also,about switching heads,know what you have first,by putting heads off a bigger motor you may end up loosing power by dropping the compression due to a larger chamber size. As mentioned,6x heads are good,rectangle port 400 ram air heads are real good,but you need the matching intake,and they are hard to find,edelbrock makes a set that are aluminum that are similar,like the super duty ports. The biggest things Ive seen for the ponts is the cam and headers,next would be intake and heads for me,oh yea,and a 4 bolt 455 would be on my hunt list also.

10-27-2004 11:08 PM

70SPORT

Quote:

Originally posted by jimfulco Make sure the 400 block has the same holes for the motor mounts that the 350 does. Pontiac used two different bolt patterns, and not all will interchange without adapters. Some have both patterns, so you might get lucky.

400's & 350's have the same stroke, 3.75". Pontiac crankshaft flanges changed a couple of times in the '60s & '70s, so be sure you have a flywheel/flexplate with a center hole that matches the crank on the 400.

the motor mounts are different however they make adapter plates for them that work very very well

10-27-2004 10:40 PM

jimfulco

Make sure the 400 block has the same holes for the motor mounts that the 350 does. Pontiac used two different bolt patterns, and not all will interchange without adapters. Some have both patterns, so you might get lucky.

400's & 350's have the same stroke, 3.75". Pontiac crankshaft flanges changed a couple of times in the '60s & '70s, so be sure you have a flywheel/flexplate with a center hole that matches the crank on the 400.

10-27-2004 03:36 PM

70SPORT

Quote:

Originally posted by Siggy_Freud There are a lot better intakes than the Torker 2. Look at a few of the others on the edelbrock line and just do some general research online.

torker 2 is great for the price...there sure are better intakes but for the money you cant beat it....my .02

Quote:

Originally posted by paperairplane Pontiac engines aren't large or small block. Externally a 326 is the same as a 455.

Put the 400 heads on the 350 and change the cam you should be good to go and save a lot of effort. Then take your time and build the 400 into a monster.

its not just a matter of switching heads...the stroke is different in a 400 vs a 350. your right externally they are the same. its more then heads and cam...In a 455 the crank shaft is way bigger as well as the bearings....forged crank in a 455.....a lot beefier

10-27-2004 03:23 PM

Siggy_Freud

There are a lot better intakes than the Torker 2. Look at a few of the others on the edelbrock line and just do some general research online.

10-27-2004 03:23 PM

paperairplane

Pontiac engines aren't large or small block. Externally a 326 is the same as a 455.

Put the 400 heads on the 350 and change the cam you should be good to go and save a lot of effort. Then take your time and build the 400 into a monster.

10-27-2004 01:32 PM

70SPORT

400 will be quite a bit better...you will have to go through it...i would put a cam in it....port the heads put on a torker 2 intake port that to match the heads........if you have money buy aluminum heads and port them......better fuel pump......700-750 double pumper carb.......rockers of your choice......just a few things that are not alot of money to produce some good horsepower......if you have time its the way to go...the aluminum heads are expensive but thats about it....if you have 6x heads thay are real good i would just port them and you should be at about 375-400 hp at the crank

10-27-2004 10:43 AM

Siggy_Freud

More cubes = more potential power. Considering both were built to the max the 400 would dominate.

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